Short wave infrared ( SWIR) spectral characteristics of alteration minerals and applications for ore exploration in Huangjindong orogenic gold deposit，northeastern Hunan

The northeastern Hunan region within the Jiangnan Orogen hosts multiple large gold deposits, constituting a significant gold metallogenic belt in China with abundant gold resources. The Huangjindong Gold Deposit, a representative deposit in this area, features substantial reserves and high- grade mineralization. Gold mineralization in this district is closely associated with hydrothermal alteration, with common alteration minerals including sericite, siderite, and montmorillonite.As an efficient exploration technique, short wave infrared (SWIR) spectroscopy enables rapid identification of alteration mineral assemblages and their relative abundances, providing critical data support for alteration mineral mapping. Methods: Based on short wave infrared spectroscopy (SWIR), this study conducted hyperspectral scanning analyses on core samples from five drill holes in the ore vein of the Huangjindong Gold Deposit. By identifying the spectral characteristics of alteration minerals and analyzing the absorption peak position (POS2200) and crystallinity (IC value) of sericite, the spatial patterns of alteration minerals in the mining area were revealed.Results: More than 10 main alteration minerals were identified, with sericite being the dominant one. The λPOS2200 values of sericite mainly range from 2196 to 2210 nm, and the DSWIR- IC values range from 0.05 to 1.96. The mean λPOS2200 and DSWIR- IC values of sericite in alteration zones from different drill holes show a gradually increasing trend from west to east.Conclusions:Research reveals significant spatial distribution patterns of alteration minerals across drill holes from west to east: The λPOS2200 value of sericite progressively increases, indicating enhanced acidity of vein- forming hydrothermal fluids; concurrently, sericite illite crystallinity (DSWIR- IC) gradually decreases, demonstrating declining fluid temperatures and confirming west- to- east migration of ore- forming fluids along the vein. A temperature attenuation model based on DSWIR- IC was established, pinpointing the hydrothermal center. This validates the model's efficacy in tracing hydrothermal pathways and locating mineralization centers, providing critical guidance for mineral exploration. The study offers novel insights for interpreting alteration signatures at the Huangjindong gold deposit and delivers a scientific foundation for regional prospecting strategies.